Technical Field
The instant disclosure relates to a capacitive touch control technique and, more particularly, to a refreshing method of sensing baseline values for a capacitive sensor device and the capacitive sensor device.
Related Art
To meet the convenience of use, more and more electronic devices adopt touch screens as controlling interfaces. Users can directly touch an image on a touch screen to control. Touch control is more convenient and more user-friendly. A touch screen includes a display for displaying and a sensor device for touch control.
Generally, the sensor device utilizes a self-capacitance sensing technique and/or a mutual capacitance sensing technique to sense if a touch is made by a user. When the sensor device senses that a capacitance at a certain coordinate position varies in a sensing procedure, the sensor device determines that the certain coordinate position is touched by a user. During operation, an untouched capacitance (a sensing baseline value) at each of coordinate positions is saved in the sensor device in advance, and then, when new capacitances (sensing values) are received, the received sensing values are compared with corresponding sensing baseline values by the sensor device to determine whether a certain coordinate position is touched.
Nevertheless, long-staying objects (water, hand, heat from fingers/hands or conductive objects stayed on the sensor device for a long time) may cause the sensor device to misjudge. During operation, the sensor device may regularly refresh the sensing baseline values. If a conductive object has contacted the sensor device for long time before the sensing baseline values are refreshed, the refreshed sensing baseline values may include capacitances caused by the long-staying object such that the refreshed baseline values are wrong bases for calculating captured signals later. If the sensor device does not refresh immediately the sensing baseline values when the long-staying objects are removed from the sensor device, a false touch is caused by the heat remained on the sensor device by the just-removed object, so that the sensor device misjudges the a false touch to be a touch event.